From: Miao Xie Subject: [PATCH 3/3] x86_64/lib: improve the performance of memmove Date: Thu, 02 Sep 2010 13:46:25 +0800 Message-ID: <4C7F3A31.4070806@cn.fujitsu.com> Reply-To: miaox@cn.fujitsu.com Mime-Version: 1.0 Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: 7bit Cc: Linux Kernel , Linux Btrfs , Linux Ext4 To: Peter Zijlstra , Ingo Molnar , Andrew Morton , "Theodore Ts'o" , Andreas Dilger Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This patch improved the performance of memmove on x86_64 by using mem_copy_bwd() instead of byte copy. But x86_64's memcpy is quite fast, so I didn't change it. I have tested this patchset by doing 500 bytes memory copy for 50000 times on my x86_64 box: memmove 2.6.36-rc1 2s 610445us 2.6.36-rc1 + patch 0s 257358us After appling this patchset, the performance of the file creation and deletion on some filesystem become better. I have tested it with the following benchmark tool on my x86_64 box. http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3 Test steps: # ./creat_unlink 50000 The result(Total time): Ext4: 2.6.36-rc1 2.6.36-rc1 + patchset file creation 0.771240 0.698983 9.4%UP file deletion 0.459065 0.425530 7.3%UP Btrfs: 2.6.36-rc1 2.6.36-rc1 + patchset file creation 0.966807 0.947592 1.9%UP file deletion 1.355671 1.217787 10.2%UP Signed-off-by: Miao Xie --- arch/x86/lib/memmove_64.c | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/lib/memmove_64.c b/arch/x86/lib/memmove_64.c index 0a33909..3640232 100644 --- a/arch/x86/lib/memmove_64.c +++ b/arch/x86/lib/memmove_64.c @@ -4,17 +4,17 @@ #define _STRING_C #include #include +#include #undef memmove void *memmove(void *dest, const void *src, size_t count) { - if (dest < src) { + if (dest - src >= count) { /* *Unsigned* compare! */ return memcpy(dest, src, count); } else { - char *p = dest + count; - const char *s = src + count; - while (count--) - *--p = *--s; + unsigned long dstp = (unsigned long)dest; + unsigned long srcp = (unsigned long)src; + mem_copy_bwd(dstp, srcp, count); } return dest; } -- 1.7.0.1